It may be desirable to measure the response of permeable subsurface formations to the flow of fluids in the pore spaces of such formations. For example, the determination of effective permeabilities of water, oil or gas, residual oil saturations, irreducible water saturations, and rock wettabilities, among other petrophysical parameters, may be very useful in gauging the producibility of hydrocarbon bearing formations. Downhole testing tools may be used for making permeability and/or other hydraulic property measurements of subsurface formations surrounding wellbores. Descriptions of such tools may be found, for example, in U.S. Pat. Nos. 5,335,542, 6,528,995, 6,856,132 and 7,032,661, the disclosures of which are incorporated herein by reference.
Various factors may restrict movement of fluid between subsurface formations and downhole testing tools. For example, during drilling of a wellbore, particles from the mud may plug the pore spaces of permeable rock formations close to the wellbore wall and create a “damaged zone” or “permeability skin” Downhole testing tools may use a perforation through a portion of the wellbore wall, for example to establish a fluid communication therethrough. Descriptions of such tools may be found, for example, in U.S. Pat. No. 7,191,831 and U.S. Patent Application Pub. Nos. 2006/0000606, 2008/0066536 and 2008/0066537, the disclosures of which are incorporated herein by reference.